Measuring device and measuring method

Abstract

A measurement device (100) includes a laser device (111), a branching section (120) that branches a laser beam into reference light and measurement light, a converging section (140) that converges the measurement light onto an object to be measured (10), a control section (160) that adjusts a focal position of the converging section (140) that converges the measurement light, and a distance calculation section (117) that calculates a distance from the object to be measured (10) based on an optical path difference between the reference light and the measurement light, wherein the converging section (140) includes a first lens (141) and a correspondence calculation section (145) that calculates a correspondence between the focal position of the converging section (140) and the position of the first lens (141) based on the position of the first lens (141) and the distance from the object to be measured (10).

Description

Technical Field

[0001] This invention relates to a measuring device and a measuring method. Background Technology

[0002] A measuring device is known for measuring distances to an object based on the time elapsed from illuminating it to receiving light reflected from it. Furthermore, a frequency-shift feedback laser (FSFL) is known as a light source for such a measuring device. This FSFL incorporates a frequency shifter in a resonator and outputs multiple longitudinal-mode lasers whose oscillation frequencies change linearly over time. Optical rangefinders using such FSFLs are also known (see, for example, Patent Document 1: Japanese Patent No. 3583906; Non-Patent Document 1: Takefumi Hara, “Distance Sensing by FSF Laser and Its Application,” Optonews, Vol. 7, No. 3, 2012, pp. 25-31 and 2; and Non-Patent Document 2: Takefumi Hara et al., “Ultra-high-precision optical measurement technology by frequency shift feedback laser,” Applied Physics, Vol. 74, No. 6, 2005). Summary of the Invention

[0003] The problem to be solved by the present invention

[0004] In such a measuring device, a converging lens can be used to focus the measuring light onto a portion of the object being measured, thereby improving the utilization efficiency of the reflected light. In this case, if the focal position of the converging lens matches the portion of the object being measured, the intensity of the received reflected light increases. On the other hand, for example, if the focal position of the converging lens deviates from the object being measured due to movement, geometry, or other reasons, the intensity of the received reflected light decreases according to the amount of deviation. Therefore, it is necessary to adjust the optical system using autofocus or similar methods to reduce the impact of deviations in the focal position of the converging lens.

[0005] The present invention was made in view of these aspects, and the object of the present invention is to rapidly adjust the optical system in order to improve the efficiency of receiving reflected light in measuring devices such as optical rangefinders.

[0006] means of solving this problem

[0007] A first aspect of the present invention provides a measuring apparatus, comprising a laser device for outputting a laser beam; a branching section for dividing the laser beam into: (i) a reference beam, which is a portion of the laser beam for illuminating a reference surface, and (ii) a measuring beam, which is at least a portion of the remaining portion of the laser beam for illuminating an object to be measured; a converging section for converging the measuring beam onto the object to be measured; a control section for adjusting the focal point position of the converging beam; and a distance calculation section for calculating the distance to the object to be measured based on the optical path difference between the reference beam reflected from the reference surface and the measuring beam reflected from the object to be measured, wherein the converging section includes a measuring beam... The system includes a first lens, a moving part that moves the first lens in the optical axis direction, a position detection part that detects the position of the first lens, and a second lens that illuminates the measurement light emitted from the first lens onto the object to be measured; a correspondence calculation part that, when the converging part focuses on the object to be measured, calculates the correspondence between the focal position of the converging part and the position of the first lens based on the position of the first lens and the distance from the object to be measured calculated by the distance calculation part, wherein the control part controls the moving part and moves the first lens to adjust the focal position of the second lens converging the measurement light.

[0008] The correspondence calculation unit can calculate the correspondence based on the difference between the positions of the first lens and the difference between the distances calculated by the distance calculation unit when the convergence part is focused on the first position and the second position on the object to be measured, respectively.

[0009] The control unit can move the first lens to satisfy the following equation calculated by the correspondence calculation unit, where f1 is the focal length of the first lens, f2 is the focal length of the second lens, d is the inter-lens distance between the first and second lenses, and z is the converging distance from the second lens to the focal point of the convergent light.

[0010]

[0011] The correspondence calculation unit can calculate the following values ​​using the following equations: a) the inter-lens distance d1 and convergence distance z1 at a first position on the object to be measured; and b) the inter-lens distance d2 and convergence distance z2 at a second position, wherein L1 is the first distance from the measuring device to the first position on the object to be measured, calculated by the distance calculation unit, and L2 is the second distance from the measuring device to the second position on the object to be measured, calculated by the distance calculation unit.

[0012]

[0013] L1-L2=z1-z2 (3).

[0014] The correspondence calculation unit can also calculate the internal optical path difference by subtracting the convergence distance z1 of the first position on the object to be measured from the first distance L1, or by subtracting the convergence distance z2 of the second position on the object to be measured from the second distance L2. The internal optical path difference represents the optical path difference between the measuring light and the reference light inside the measuring device.

[0015] The correspondence calculation unit can calculate the correspondence based on the internal optical path difference between the reference light and the measurement light inside the measuring device, the position of the first lens, and the distance calculated by the distance calculation unit when the converging part is focused on the object to be measured at the first position.

[0016] The measuring device also includes a storage unit that stores information about the geometry of the object to be measured, wherein the control unit can determine the position where the measuring light is to be focused based on the correspondence and the information about the geometry of the object to be measured.

[0017] The distance calculation unit also includes an error calculation unit. When calculating the distance to the object to be measured, the error calculation unit calculates the error of the focal position of the converging part based on the detection result and correspondence of the position of the first lens, and outputs the distance calculation result and the focal position calculation error in a correlated manner.

[0018] The measuring device also includes an interference detection unit that detects interference signals based on the optical path difference between the reference light and the measurement light. The distance calculation unit includes an order determination unit that determines the interference order of the interference signals based on the correspondence calculated by the correspondence calculation unit. The distance calculation unit can calculate the distance to the object to be measured based on the detected interference signals and the determined interference order.

[0019] A second aspect of the present invention provides a measurement method comprising the following steps: outputting a laser beam, dividing the laser beam into: (i) a reference beam, which is a portion of the laser beam for illuminating a reference surface, and (ii) a measurement beam, which is at least a portion of the remaining portion of the laser beam for illuminating an object to be measured; focusing the measurement beam onto the object to be measured by using a converging portion having a first lens and a second lens; calculating a distance to the object to be measured based on the optical path difference between the reference beam reflected from the reference surface and the measurement beam reflected from the object to be measured; calculating a correspondence between the focal position of the converging portion and the position of the first lens based on the position of the first lens and the calculated distance to the object to be measured, wherein converging includes allowing the measurement beam to enter the first lens, illuminating the measurement beam emitted from the first lens toward the object to be measured through the second lens, moving the first lens such that the focal position of the second lens converging the measurement beam is aligned with the object to be measured, and detecting the position of the first lens.

[0020] Effects of the present invention

[0021] According to the present invention, the optical system of a measuring device, such as an optical rangefinder, can be quickly adjusted. Attached Figure Description

[0022] Figure 1 An example configuration of the measuring device 100 according to this embodiment and the object to be measured 10 are shown;

[0023] Figure 2 This is a flowchart illustrating an example of the operation of the measuring device 100 according to this embodiment;

[0024] Figure 3 An example is shown of the correspondence between the focal position of the converging portion 140 calculated by the correspondence calculation unit 145 and the position of the first lens 141 according to this embodiment;

[0025] Figure 4 This is a flowchart illustrating a variant example of the operation of the measuring device 100 according to this embodiment;

[0026] Figure 5 A variant example of the measuring device 100 according to this embodiment and the object to be measured 10 are shown. Detailed Implementation

[0027] <Configuration example of measuring device 100>

[0028] Figure 1 An example configuration of the measuring device 100 according to this embodiment and a measurement object 10 are shown. The measuring device 100 measures the distance from the measuring device 100 to the measurement object 10. The measuring device 100 measures the distance to one or more locations on the measurement object 10. The measuring device 100 can measure distances to multiple locations on the measurement object 10 to measure the geometry of the measurement object 10, for example. The measurement object 10 is, for example, a solid, such as a semiconductor wafer including Si, GaAs, GaN, etc., a high-precision mirror, metal, or resin. The measuring device 100 includes an interferometer 110, a branch 120, a reference surface 130, a convergence section 140, a storage section 150, a control section 160, and a display section 170.

[0029] Interferometer 110 outputs a laser beam and detects the interference of the laser beam reflected from the object to be measured 10 and the reference surface 130. Interferometer 110 includes a laser device 111, a magnifying lens 112, a collimating lens 113, a beam splitter 114, an image forming lens 115, an interference detection unit 116, and a distance calculation unit 117. It should be noted that... Figure 1 The configuration of the interferometer 110 shown is an example and is not limited thereto, and can be any configuration used to calculate distance by detecting the interference of the laser beam.

[0030] Laser device 111 outputs a laser beam. Laser device 111 has a laser resonator and, for example, outputs a frequency-modulated laser beam having multiple modes. In this case, laser device 111 has a frequency shifter arranged in the resonator and outputs multiple longitudinal-mode lasers whose oscillation frequencies change linearly with time. As an example, laser device 111 is a frequency-shift feedback laser. Since frequency-shift feedback lasers are known as described in Non-Patent Document 1 and Non-Patent Document 2, a detailed description thereof is omitted here.

[0031] The magnifying lens 112 enlarges the diameter of the light output from the laser device 111. The collimating lens 113 collimates the light incident from the magnifying lens 112 and outputs collimated light. Furthermore, light reflected from the object to be measured 10 and the reference surface 130 enters the collimating lens 113, and the collimating lens 113 emits light generated by reducing the diameter of the incident light, thereby transmitting the light to the beam splitter 114.

[0032] Beam splitter 114 reflects portions of the measurement light and reference light emitted from collimating lens 113 toward interferometric detection unit 116. Beam splitter 114 includes, for example, a half-reflecting mirror. Image forming lens 115 forms an image of the light reflected by beam splitter 114 on interferometric detection unit 116. That is, image forming lens 115 provides the interferometric detection unit 116 with the interference signal generated by the interference of measurement light and reference light.

[0033] The interference detection unit 116 detects the interference signal based on the optical path difference between the reference light and the measurement light. The interference detection unit 116 also detects the light intensity level of the interference signal based on both the reference light and the measurement light. The interference detection unit 116 can be, for example, an imaging element used to detect the interference signal as an image. The interference detection unit 116 can be an optical detector, such as a photodetector.

[0034] The distance calculation unit 117 calculates the distance to the object to be measured 10 based on the optical path difference between the reference light reflected by the reference surface 130 and the measurement light reflected by the object to be measured 10. For example, the distance calculation unit 117 calculates the distance to the object to be measured corresponding to the phase difference of the interference signal. The distance calculation unit 117 can calculate the distance to the object to be measured 10 using known operations as described in Non-Patent Document 2, and a detailed description thereof is omitted here.

[0035] The distance calculation unit 117 can calculate the absolute distance corresponding to the optical path difference between the reference light and the measuring light. Furthermore, the distance calculation unit 117 can calculate the distance obtained by adding a predetermined offset distance to the calculated absolute distance. The offset distance is a value that determines the position used as a reference in distance measurements performed by the measuring device 100.

[0036] Branch 120 splits the laser beam into (i) a reference beam, which is a portion of the laser beam and is used to illuminate the reference surface 130; and (ii) a measurement beam, which is at least a portion of the remaining portion of the laser beam and is used to illuminate the object to be measured 10. Furthermore, branch 120 returns the reference beam reflected by the reference surface 130 and the measurement beam reflected by the object to be measured 10 to the interferometer 110. Branch 120 is, for example, a beam splitter.

[0037] Reference surface 130 reflects the laser beam incident from branch 120. Reference surface 130 preferably has a reflective surface that allows total internal reflection of the laser beam. It should be noted that reference surface 130 may be disposed between interferometer 110 and converging portion 140. In this case, for example, reference surface 130 is a semi-reflective mirror, which serves as branch 120 that reflects a portion of the laser beam and transmits a portion of the remaining laser beam.

[0038] The converging section 140 includes multiple lenses and converges the measurement light onto the object to be measured 10. Figure 1 An example of a converging section 140 including two lenses is shown. The converging section 140 includes a first lens 141, a moving section 142, a second lens 143, a position detection section 144, and a correspondence calculation section 145.

[0039] Measurement light from interferometer 110 enters first lens 141. As an example, first lens 141 is a concave lens, which increases the spot size of the incident measurement light. First lens 141 is configured to be movable along the optical axis. By moving first lens 141, the focal point position of the converging portion 140 changes in the optical axis direction. When first lens 141 moves toward the object to be measured 10, the focal point position of the converging portion 140 changes, for example, in a direction away from the converging portion 140.

[0040] The moving part 142 moves the first lens 141 in the optical axis direction. The moving part 142 moves the first lens 141 in response to a control signal from the control part 160. For example, the moving part 142 is an actuator such as a motor.

[0041] The second lens 143 illuminates the measuring light emitted from the first lens 141 toward the object to be measured 10. Furthermore, the second lens 143 converges the measuring light reflected from the object to be measured 10 so that it illuminates the first lens 141. The second lens 143 is, for example, a lens that is fixed in position along the optical axis. The second lens 143 is, for example, a convex lens.

[0042] The position detection unit 144 detects the position of the first lens 141. For example, the position detection unit 144 detects the position of the first lens 141 in the optical axis direction. In this case, the position detection unit 144 detects the distance between the first lens 141 and the second lens 143 as the position of the first lens 141 relative to the second lens 143. Here, the distance between the first lens 141 and the second lens 143 is defined as the inter-lens distance d. It should be noted that the inter-lens distance d detected by the position detection unit 144 can be a relative value.

[0043] When the converging section 140 focuses on the object to be measured 10, the correspondence calculation unit 145 calculates the correspondence between the focal position of the converging section 140 and the position of the first lens 141, based on the position of the first lens 141 and the distance from the object to be measured calculated by the distance calculation unit 117. The focal position of the converging section 140 is the distance from the second lens 143 to the focal point, for example, with the second lens 143 as a reference. Here, the distance from the second lens 143 to the focal point is defined as the convergence distance z. That is, the correspondence calculation unit 145 calculates the correspondence between the convergence distance z and the inter-lens distance d.

[0044] The storage unit 150 stores the calculation results of the corresponding calculation unit 145. The storage unit 150 can also store information about the geometry of the object to be measured 10. Furthermore, the storage unit 150 can store intermediate data, calculation results, thresholds, parameters, etc., generated (or used) by the measuring device 100 during operation. In addition, the storage unit 150 can provide stored data to the requester in response to requests from each part of the measuring device 100.

[0045] The control unit 160 controls the operation of the measuring device 100. The control unit 160 controls the interferometer 110 and the converging unit 140 to converge the measurement light output from the interferometer 110 and focus it onto a portion of the object 10 to be measured. Additionally, the control unit 160 controls the interferometer 110 and the display unit 170, and displays the measurement results of the interferometer 110 on the display unit 170.

[0046] For example, the control unit 160 adjusts the focal position of the converging unit 140 to converge the light. The control unit 160 controls the moving unit 142 to move the first lens 141 to adjust the focal position of the second lens 143 to converge the measurement light. For example, the control unit 160 moves the first lens 141 based on the correspondence between the convergence distance z and the inter-lens distance d. As an example, based on the determination of the convergence distance z corresponding to the convergence position, the control unit 160 moves the first lens 141 to a position where the inter-lens distance d corresponds to the convergence distance z. The control unit 160 can move the first lens 141 based on the geometry of the object 10 to be measured. Furthermore, the control unit 160 can specify the convergence distance z corresponding to the position of the first lens 141 based on the determination of the position of the first lens 141.

[0047] Furthermore, the control unit 160 can move the first lens 141 based on the calculated distance to the object 10 to be measured obtained by the calculation unit 117. For example, the control unit 160 moves the first lens 141 to a lens distance d corresponding to the convergence distance z, which corresponds to the calculated distance. Additionally, the control unit 160 can move the first lens 141 based on the amplitude of the interference signal detected by the interference detection unit 116. The control unit 160 can move the first lens 141 to increase the intensity of the received light for measurement; in this case, the operation of the control unit 160 serves as an autofocus operation.

[0048] The control unit 160 can store the correspondence calculated by the correspondence calculation unit 145 in the storage unit 150. Furthermore, the control unit 160 can store the measurement results of the measuring device 100 in the storage unit 150. The control unit 160 can also store the measurement results of the measuring device 100 in an external database, etc. In this case, the control unit 160 is preferably connected to a network, etc.

[0049] The display unit 170 includes a monitor and displays the measurement results of the interferometer 110. Furthermore, the display unit 170 can display the status and process of the control operations of the control unit 160. The display unit 170 can receive control commands from users and provide these control commands to the control unit 160.

[0050] The measuring apparatus 100 according to this embodiment focuses the measuring light onto a portion of the surface of the object to be measured 10 via the converging section 140, thereby measuring the distance to the object to be measured 10 by improving the efficiency of receiving reflected light. In this case, movement or changes in the object to be measured 10, as well as complex or fine geometry, cause the focal position of the converging section 140 to deviate relative to the object to be measured 10, which reduces the efficiency of receiving reflected light.

[0051] Therefore, the automatic focusing operation of the measuring device 100 can be performed to improve the intensity of the received light from the reflected light; however, the automatic focusing operation can sometimes take a long time. Here, it is conceivable to pre-set the lens positions as references for multiple lenses to speed up the automatic focusing operation. However, such a default setting requires measuring the inter-lens distance d using a separate device different from the measuring device 100, or performing prior focus adjustment by accurately arranging the reference positions and the object to be measured 10, which is time-consuming. In particular, it is difficult to perform such a default setting for each moving position when the measuring device 100 is moved for measurement.

[0052] Therefore, the measuring device 100 according to this embodiment uses the measurement results of the measuring device 100 itself to obtain the correspondence between the convergence distance z and the inter-lens distance d, which makes it easy to focus on the surface of the object to be measured 10 without performing such a default setting. This operation of the measuring device 100 will be described below.

[0053] <Operational Example of Measuring Device 100>

[0054] Figure 2 This is a flowchart illustrating an example of the operation of the measuring device 100 according to this embodiment. The measuring device 100 performs settings for the measurement operation by executing operations from step S210 to step S280. The measuring device 100 may perform the operations from step S210 to step S280 as a default setting, or these operations may be performed before measuring the distance.

[0055] First, the object to be measured 10 is placed within the measurable range of the measuring device 100 (S210). Then, the measuring device 100 performs focusing by converging the measuring light at the first position onto the object to be measured 10 (S220). The first position on the object to be measured 10 may be a predetermined part of the surface of the object to be measured 10, or alternatively, an area determined by a user or the like. The first position on the object to be measured 10 serves as a reference position relative to the converging portion 140.

[0056] For example, laser device 111 outputs a laser beam, and branch 120 splits the laser beam into: (i) a reference beam, which, as part of the laser beam, is used to illuminate a reference surface 130; and (ii) a measurement beam, which, as at least a portion of the remaining portion of the laser beam, is used to illuminate the object to be measured 10. Measurement device 100 then uses converging portion 140 to focus the measurement beam onto the object to be measured 10. Converging portion 140 allows the measurement beam to enter a first lens 141 and illuminates the object to be measured 10 from a second lens 143. Measurement device 100 then moves the first lens 141 such that the focal position of the second lens 143, used to converge the measurement beam, is aligned with the object to be measured 10.

[0057] For example, the measuring device 100 uses an autofocus function to focus the measuring light onto a first position. This autofocus function is performed, for example, by the control unit 160. Here, the distance from the second lens 143 to the focal point aligned with the first position is defined as the convergence distance z1.

[0058] Then, the position detection unit 144 detects the position of the first lens 141 (S230). The position detection unit 144 detects the inter-lens distance between the first lens 141 and the second lens 143. Here, the inter-lens distance d1 is defined when the converging unit 140 is focused on the object 10 to be measured at a first position.

[0059] Next, based on the optical path difference between the reference light reflected from the reference surface and the measurement light reflected from the object to be measured 10, the distance calculation unit 117 calculates the distance to the object to be measured 10 (S240). The distance calculation unit 117 calculates the distance to the first position in response to focusing the measurement light on the object to be measured 10. Here, the distance calculated by the distance calculation unit 117 is, for example, an absolute distance, which corresponds to the optical path difference between the measurement light and the reference light.

[0060] exist Figure 1 In this context, the distance from branch 120 to reference surface 130 is defined as L. ref The distance from branch 120 to the second lens 143 is defined as L. lens When the converging section 140 is focused on the first position on the object to be measured 10, the optical path difference between the measuring light and the reference light is 2(L). Lens +z1-L ref Assuming the absolute distance from the measuring device 100 to the first position is a first distance L1, then the first distance L1 is (L... Lens +z1-L ref Here, (L) Lens -L ref ) is the internal optical path difference of the measuring device 100.

[0061] Next, the measuring device 100 converges and focuses the measuring light onto a second position on the object to be measured 10 (S250). The second position on the object to be measured 10 may, for example, be a portion of the surface of the object to be measured 10 predetermined when the object to be measured 10 moves in the optical axis direction, or alternatively, it may be an area determined by a user or the like. After movement, the second position on the object to be measured 10 may be substantially equal to the first position on the object to be measured 10, or it may be different from the first position. Furthermore, when the position of the object to be measured 10 remains unchanged, the second position on the object to be measured 10 may differ from the first position.

[0062] Therefore, the first position and the second position can be any positions at different distances from the converging portion 140. It should be noted that the first position and the second position are preferably predetermined such that the difference in inter-lens distance relative to each position is as large as possible. The measuring device 100 focuses the measuring light at the second position using the same operation as focusing the measuring light at the first position. Here, the distance from the second lens 143 to the focal position aligned with the first position is defined as the convergence distance z2.

[0063] Then, the position detection unit 144 detects the position of the first lens 141 (S260). The position detection unit 144 detects the inter-lens distance between the first lens 141 and the second lens 143. Here, the inter-lens distance when the converging unit 140 focuses on the second position of the object to be measured 10 is defined as d2.

[0064] Then, the distance calculation unit 117 calculates the distance to the object to be measured 10 (S270). In response to focusing the measuring light onto the object to be measured 10 at a second position, the distance calculation unit 117 calculates the distance to the second position using the same operation as calculating the distance to the first position. Here, the distance from the measuring device 100 to the second position is defined as the second distance L2. The second distance L2 is, for example, L Lens +z2-L ref .

[0065] Next, based on the position of the first lens 141 and the calculated distance to the object to be measured 10, the correspondence calculation unit 145 calculates the correspondence between the focal position of the converging part 140 and the position of the first lens 141 (S280). It should be noted that the focal position of the converging part 140 is the convergence distance z from the second lens 143 to the focal point of the converging part 140. In this embodiment, when the converging part 140 is focused on the first position and the second position on the object to be measured 10, respectively, the correspondence calculation unit 145 calculates the correspondence based on the difference between these positions of the first lens 141 and the difference between these distances calculated by the distance calculation unit 117. A specific method for calculating the correspondence will be described.

[0066] <Example of the derivation of correspondence>

[0067] Here, assuming the focal length of the first lens 141 is f1 and the focal length of the second lens 143 is f2, the combined focal length F and the convergence distance z of the converging section 140 are expressed by the following equations. For example, design values ​​are used for the focal lengths of the first lens 141 and the second lens 143.

[0068] [Equation 1]

[0069]

[0070] [Equation 2]

[0071]

[0072] From [Equation 1] and [Equation 2], the relationship between the inter-lens distance d and the convergence distance z is expressed by the following equation.

[0073] [Equation 3]

[0074]

[0075] With the focal point located at the first position and the second position respectively, the following equation is obtained by substituting the inter-lens distance and the convergence distance into [Equation 3] and calculating the difference. Here, d1-d2 on the left is the difference between the positions of the first lens 141, which can be calculated from the measurement results of the measuring device 100. Therefore, the position of the first lens 141 detected by the position detection unit 144 can be a relative value.

[0076] [Equation 4]

[0077]

[0078] Furthermore, the difference in distance calculated by the distance calculation unit 117 is expressed as the following equation, and the left side L1-L2 can be calculated based on the measurement results achieved by the measuring device 100.

[0079] [Equation 5]

[0080] L1-L2=z1-z2

[0081] Based on the simultaneous equations [Equation 4] and [Equation 5], the values ​​of convergence distances z1 and z2 can be calculated. Therefore, the correspondence calculation unit 145 can calculate, based on the measurement results achieved by the measuring device 100, the values ​​of: i) the inter-lens distance d1 and convergence distance z1 in the first position; and ii) the inter-lens distance d2 and convergence distance z2 in the second position, which satisfy [Equation 3]. Furthermore, the correspondence calculation unit 145 can calculate the internal optical path difference (L... Lens -Lref Therefore, since the correspondence calculation unit 145 can specify the inter-lens distance and convergence distance at the reference position, the correspondence calculation unit 145 can calculate the inter-lens distance d relative to the unknown convergence distance z or the absolute distance L based on [Equation 3].

[0082] <Example of correspondence>

[0083] Figure 3 An example is shown of the correspondence between the focal position of the converging portion 140 calculated by the correspondence calculation unit 145 and the position of the first lens 141 according to this embodiment. Figure 3 The horizontal axis represents the convergence distance z, and the vertical axis represents the distance d between the lenses. Figure 3 An example is shown where the focal length f1 of the first lens 141 is assumed to be -10mm, and the focal length f2 of the second lens 143 is assumed to be 100mm. The correspondence calculation unit 145 stores the calculated correspondence in the storage unit 150. (Refer to...) Figure 3 It should be noted that the smaller the convergence distance z, the greater the change in the inter-lens distance d. Therefore, it is preferable to set reference positions, such as the first position and the second position, closer to the convergence section 140.

[0084] As part of the distance measurement operation, the measuring device 100 according to this embodiment calculates the distance d relative to the convergence distance z or the absolute distance L. Therefore, for example, when a convergence position z' of the light to be converged by the converging part 140 is found, the measuring device 100 can specify the inter-lens distance d' corresponding to the convergence position z'. In this case, for example, the control unit 160 can quickly move the first lens 141 to a position corresponding to the inter-lens distance d' to converge the measurement light at the convergence position z'.

[0085] If information about the geometry of the object to be measured 10 is stored in a storage unit 150 or similar, or if the information about the geometry of the object to be measured 10 is provided externally, the actual geometry of the object to be measured 10 can be measured, for example, by sequentially measuring multiple positions on the object to be measured 10 using the measuring device 100. There are cases where, for example, after manufacturing the object to be measured 10 based on design values ​​related to its geometry, the geometry of the object to be measured 10 should be inspected or examined. In this case, if the focal position is determined by sequentially performing an autofocus operation at multiple positions on the object to be measured 10, the measurement time becomes longer.

[0086] However, according to the measuring apparatus 100 of this embodiment, the control unit 160 can determine the position for focusing the measuring light based on information and correspondence related to the geometry of the object to be measured 10. For example, a first position on the object to be measured 10 is determined in association with a predetermined reference position in the information about the geometry of the object to be measured 10. Therefore, this allows the next measurement position of the object to be measured 10 to be determined based on the information about the geometry of the object to be measured 10, and the measuring apparatus 100 can quickly converge the measuring light by specifying the corresponding position of the first lens 141 by determining the next measurement position as the convergence position of the measuring light.

[0087] Therefore, the measuring device 100 can measure the geometry of the object to be measured 10 by sequentially measuring multiple positions on the object 10 based on previously calculated correspondences, without performing an autofocus operation. In this way, the measuring device 100 can quickly and sequentially focus the measuring light onto the appropriate position on the object 10 for each position to be measured.

[0088] It should be noted that the measuring device 100 can measure the geometry of an object different from the object to be measured 10 after calculating the correspondence between the focal position of the converging portion 140 and the position of the first lens 141 using the object to be measured 10. In this case, the different object preferably has the same geometry as the object to be measured 10 and is preferably arranged in the same manner as the object to be measured 10. Furthermore, even if the different object has a different geometry than the object to be measured 10, the measuring device 100 can measure the geometry of the different object using a calculated correspondence similar to that of the object to be measured 10 by acquiring information about the distance between at least one position in the geometry and a reference position (e.g., a first position on the object to be measured 10). In addition, when a predetermined number of distance measurements are completed, or when a predetermined time has elapsed, the measuring device 100 can calculate the correspondence between the focal position of the converging portion 140 and the position of the first lens 141.

[0089] In the measuring apparatus 100 according to the present embodiment described above, an example has been described of calculating the correspondence between the focal position of the converging portion 140 and the position of the first lens 141 by converging the measuring light at two reference positions; however, the calculation is not limited to this. The measuring apparatus 100 can calculate this correspondence based on information about the internal optical path difference and by converging the measuring light at a reference position. The operation of the measuring apparatus 100 will be described.

[0090] <Example of a variation in the operation of measuring device 100>

[0091] Figure 4This is a flowchart illustrating a variant example of the operation of the measuring device 100 according to this embodiment. The measuring device 100 performs the setting of the measurement operation by executing the operations from step S410 to step S460.

[0092] First, the object to be measured 10 is placed within the measurable range of the measuring device 100 (S410). Then, the measuring device 100 converges and focuses the measuring light onto a first position on the object to be measured 10 (S420). Next, the position detection unit 144 detects the position of the first lens 141 (S430). The distance calculation unit 117 then calculates the distance to the object to be measured 10 (S440). The operation from step S410 to step S440 can be performed in conjunction with the operation from... Figure 2 The operations from step S210 to step S240 are the same, and their descriptions are omitted here.

[0093] Next, the correspondence calculation unit 145 obtains information about the internal optical path difference of the measuring device 100 (S450). Here, the internal optical path difference is the optical path difference between the reference light and the measuring light inside the measuring device 100, and as an example, the internal optical path difference is (L Lens -L ref The storage unit 150 can store information about the pre-measured internal optical path difference, and the correspondence calculation unit 145 can read and obtain information about the internal optical path difference from the storage unit 150, for example.

[0094] For example, the internal optical path difference essentially matches the optical path difference between the light reflected from the lens surface of the second lens 143 and the reference light. Therefore, as an example, the internal optical path difference can be measured by providing a reflective member or the like on a portion of the lens surface of the second lens 143. In this case, the correspondence calculation unit 145 can obtain the absolute distance calculated by the distance calculation unit 117 as the internal optical path difference. It should be noted that the reflective member is preferably a member that can be detached from the surface of the second lens 143. The reflective member is, for example, a reflective film.

[0095] Alternatively, the design values ​​of the optical system can be pre-stored in the storage unit 150 as an internal optical path difference, or the values ​​measured by another measuring device or instrument can be pre-stored in the storage unit 150. It should be noted that the operation of step S450 does not need to follow the operations from step S410 to step S440; therefore, it can be performed before the operation of step S410, between the operations from step S410 to step S440, or in parallel with any operation from step S410 to step S440.

[0096] Next, when the converging section 140 focuses on the first position on the object 10 to be measured, the correspondence calculation unit 145 calculates the correspondence based on the acquired internal optical path difference, the position of the first lens 141, and the distance calculated by the distance calculation unit 117 (S460). The correspondence calculation unit 145 can, for example, calculate the correspondence based on the internal optical path difference (L... Lens -L ref ) and the first distance L1 (i.e. L Lens +z1-L ref The convergence distance z1 is calculated using [Equation 3]. Then, the inter-lens distance d1 corresponding to the convergence distance z1 can be calculated using [Equation 3].

[0097] In this way, the correspondence calculation unit 145 can obtain the internal optical path difference (L) at the first position. Lens -L ref The inter-lens distance d1 and the convergence distance z1 are calculated. Therefore, the correspondence calculation unit 145 can express the unknown inter-lens distance d as the amount of movement from the inter-lens distance d1 at the first position, and thus calculate the absolute distance L or the convergence distance z relative to the inter-lens distance d based on [Equation 3]. That is, even when performing the operation according to this variant, the measuring device 100 can calculate the correspondence between the focal position of the convergence unit 140 and the position of the first lens 141.

[0098] In the measuring apparatus 100 according to this embodiment, an example is given of measuring the geometry of the object to be measured 10 by calculating the correspondence between the focal position of the converging section 140 and the position of the first lens 141 based on correspondence, but the measurement is not limited to this. The measuring apparatus 100 can evaluate the amount of defocusing in the autofocus operation based on the calculated correspondence, and can calculate the order of interference of the interference detection section 116. This measuring apparatus 100 will be described below.

[0099] <Example of a variation of measuring device 100>

[0100] Figure 5 A variant example of the measuring apparatus 100 according to this embodiment, together with the object to be measured 10, is shown. In the measuring apparatus 100 of this variant example, the same reference numerals are assigned to components having substantially the same operation as those in the measuring apparatus 100 according to this embodiment, such as... Figure 1 As shown, and its description omitted. In the measuring device 100 of this variant example, the distance calculation unit 117 includes an error calculation unit 180 and a sequence determination unit 190. Needless to say, the measuring device 100 can be configured such that the distance calculation unit 117 includes either the error calculation unit 180 or the sequence determination unit 190.

[0101] As described above, the error calculation unit 180 acquires the correspondence between the focal position of the converging section 140 and the position of the first lens 141 calculated by the corresponding calculation unit 145. When calculating the distance to the object to be measured 10, the error calculation unit 180 calculates the error of the focal position of the converging section 140 based on the detection result of the position of the first lens 141 and the acquired correspondence. For example, consider the case where the control unit 160 uses an autofocus operation to align the converging position of the converging section 140 and measure the distance to the object to be measured 10.

[0102] For example, the error calculation unit 180 acquires information about the position d” of the first lens 141 automatically adjusted by the control unit 160 and the absolute distance L” calculated by the distance calculation unit 117. Additionally, the error calculation unit 180 acquires information about the convergence distance z0 corresponding to the position d” of the first lens 141 from the correspondence stored in the storage unit 150. The error calculation unit 180 adds the internal optical path difference to the convergence distance z0 to calculate the exponent L0 of the absolute distance. Then, the error calculation unit 180 sets Δz (the difference between the calculated absolute distance L” and the exponent L0) as the defocusing amount (error) for the autofocus operation.

[0103] Therefore, when performing autofocus operation, the error calculation unit 180 calculates the error Δz of the focal position, and the distance calculation unit 117 outputs the distance calculation result L” and the calculated focal position error Δz in a mutually related manner. Thus, the user of the measuring device 100 can know the error Δz and determine the state of the measuring device 100 based on, for example, the magnitude of the error Δz and its change over time. In this embodiment, the calculation result Δz of the error calculation unit 180 is described as the error of the focal position, but it does not necessarily mean a strict measurement error; for example, Δz is used as an indication of the error in the focusing operation.

[0104] In this embodiment, an example of the error calculation unit 180 calculating the error value is described, but the present disclosure is not limited thereto. The storage unit 150 may store: i) the correspondence between information about the distance calculation result and information related to the error in the detected position of the first lens 141, or ii) the correspondence between information about the distance calculation result and information about the error range, for example. Therefore, when the measuring device 100 performs an autofocus operation, the error calculation unit 180 can quickly identify and output the corresponding error based on the calculated distance to the object to be measured 10 and the detected position of the first lens 141.

[0105] The sequence determination unit 190 determines the interference order of the interference signals based on the correspondence calculated by the correspondence calculation unit 145. Since the intensity change of the interference signal repeats with the period of the interference wave, there can be multiple solutions for the distance calculated by the distance calculation unit 117. Therefore, a method for determining the interference order of the interference signals by repeating the distance measurement twice is known (Non-Patent Document 2).

[0106] However, since the measuring device 100 according to this embodiment calculates the correspondence between the focal position of the converging portion 140 and the position of the first lens 141, the focal position of the converging portion 140 can be specified based on the detection result of the position of the first lens 141. Since the focal position of the converging portion 140 substantially corresponds to the position of the object to be measured 10, the focal position can be converted into a distance from the object to be measured 10 within one cycle of the interference wave. Therefore, the sequence determination unit 190 can determine the order of the interference signals based on the determination of the position of the first lens 141. Therefore, the distance calculation unit 117 can calculate the distance from the object to be measured 10 based on the interference signals detected by a single distance measurement and the determined order of interference.

[0107] The distance calculation unit 117, correspondence calculation unit 145, storage unit 150, and control unit 160 described in this embodiment are, for example, formed by integrated circuits. In this case, at least a portion of the distance calculation unit 117, correspondence calculation unit 145, storage unit 150, and control unit 160 includes a field-programmable gate array (FPGA), a digital signal processor (DSP), and / or a central processing unit (CPU).

[0108] When a computer or the like is used as the distance calculation unit 117, the correspondence calculation unit 145, and the control unit 160, the storage unit 150 can store the operating system (OS) and programs used to operate the computer or the like. Furthermore, the storage unit 150 can store various types of information, including databases referenced when executing programs. For example, the computer uses the distance calculation unit 117, the correspondence calculation unit 145, and the control unit 160 by executing programs stored in the storage unit 150.

[0109] For example, storage unit 150 includes read-only memory (ROM) for storing the basic input / output system (BIOS) of a computer and random access memory (RAM) as the working area. Furthermore, storage unit 150 may include high-capacity storage devices such as hard disk drives (HDDs) and / or solid-state drives (SSDs). In addition, the computer may further include a graphics processing unit (GPU), etc.

[0110] The present invention has been described based on exemplary embodiments. The scope of the present invention is not limited to the scope described in the above embodiments; various changes and modifications can be made within the scope of the present invention. For example, all or part of the device can be configured to be functionally or physically distributed and integrated in any unit. Furthermore, new exemplary embodiments resulting from any combination thereof are included in the exemplary embodiments of the present invention. The effects of the new embodiments resulting from the combination have the same effects as the original embodiments.

[0111] [Description of reference numerals in the attached figures]

[0112] 10. Object to be measured

[0113] 100 Measuring device

[0114] 110 interferometer

[0115] 111 Laser Device

[0116] 112 Magnifying Lens

[0117] 113 Collimating Lens

[0118] 114 beam splitter

[0119] 115 Imaging Lens

[0120] 116 Interference Detection Department

[0121] 117 Distance Calculation Department

[0122] 120 Branch

[0123] 130 Reference Surface

[0124] 140 Convergence Department

[0125] 141 First Lens

[0126] 142 Mobile Department

[0127] 143 Second Lens

[0128] 144 Position Detection Department

[0129] 145 Correspondence Calculation Unit

[0130] 150 Storage Unit

[0131] 160 Control Department

[0132] 170 Display Section

[0133] 180 Error Calculation Department

[0134] 190 Sequence Determination Department

Claims

1. A measuring device, comprising: A laser device that outputs a laser beam; The branch divides the laser beam into: (i) a reference beam, which is a part of the laser beam, for illuminating a reference surface, and (ii) a measurement beam, which is at least a part of the remaining portion of the laser beam, for illuminating the object to be measured; The converging section focuses the measuring light onto the object to be measured. The control unit adjusts the focal position of the convergence unit to converge the measurement light. The interference detection unit detects the interference signal based on the optical path difference between the reference light reflected by the reference surface and the measurement light reflected by the object to be measured; and The distance calculation unit calculates the distance to the object to be measured, which corresponds to the phase difference of the interference signal, wherein... The convergence section includes: The first lens is through which the measuring light enters. The moving part moves the first lens along the optical axis. The position detection unit detects the position of the first lens. The second lens directs the measuring light emitted from the first lens toward the object to be measured. A correspondence calculation unit, when the converging part is focused on the object to be measured, calculates the correspondence between the focal position of the converging part and the position of the first lens based on the position of the first lens and the distance from the object to be measured calculated by the distance calculation unit, wherein... The control unit controls the moving unit and moves the first lens to adjust the focal position of the second lens that converges the measurement light, while maintaining a constant internal optical path difference, which represents the optical path difference between the optical path of the measurement light from the branch to the second lens and the optical path of the reference light from the branch to the reference surface.

2. The measuring device according to claim 1, wherein, The correspondence calculation unit can calculate the correspondence based on the difference between the positions of the first lens and the difference between the distances calculated by the distance calculation unit when the convergence part is focused on the first position and the second position on the object to be measured, respectively.

3. The measuring device according to claim 1, wherein... The control unit moves the first lens to satisfy the following equation calculated by the correspondence calculation unit, wherein... f1 is the focal length of the first lens, f2 is the focal length of the second lens, d is the distance between the first and second lenses, and z is the converging distance from the second lens to the focal point where the measured light converges. 。 4. The measuring device according to claim 3, wherein The correspondence calculation unit uses the following equations to calculate the following values: a) the inter-lens distance d1 and convergence distance z1 at a first position on the object to be measured; and b) the inter-lens distance d2 and convergence distance z2 at a second position, wherein L1 is the first distance from the measuring device to the first position on the object to be measured, calculated by the distance calculation unit, and L2 is the second distance from the measuring device to the second position on the object to be measured, calculated by the distance calculation unit. ； 。 5. The measuring device according to claim 4, wherein The correspondence calculation unit also calculates the internal optical path difference by subtracting the convergence distance z1 of the first position on the object to be measured from the first distance L1, or by subtracting the convergence distance z2 of the second position on the object to be measured from the second distance L2. The internal optical path difference represents the optical path difference between the measuring light and the reference light inside the measuring device.

6. The measuring device according to claim 1, wherein... The correspondence calculation unit calculates the correspondence based on the internal optical path difference between the reference light and the measurement light inside the measuring device, the position of the first lens, and the distance calculated by the distance calculation unit when the converging unit focuses on the first position on the object to be measured.

7. The measuring device according to claim 1, further comprising: The storage unit stores information about the geometry of the object to be measured, wherein... The control unit determines the focal point of the measuring light based on this correspondence and information about the geometry of the object to be measured.

8. The measuring device according to claim 1, wherein The distance calculation unit also includes: The error calculation unit calculates the error of the focal position of the converging part based on the detection result and correspondence of the position of the first lens when calculating the distance to the object to be measured, and the distance calculation unit outputs the distance calculation result and the focal position calculation error in a correlated manner.

9. The measuring device according to any one of claims 1 to 8, wherein The distance calculation unit includes a sequence determination unit that determines the interference order of the interference signals based on the correspondence calculated by the correspondence calculation unit, and the distance calculation unit calculates the distance to the object to be measured based on the detected interference signals and the determined interference order.

10. A measuring device, comprising: A laser device that outputs a laser beam; The branch divides the laser beam into: (i) a reference beam, which is a part of the laser beam, for illuminating a reference surface, and (ii) a measurement beam, which is at least a part of the remaining portion of the laser beam, for illuminating the object to be measured; The converging section focuses the measuring light onto the object to be measured. The control unit adjusts the focal position of the convergence unit to converge the measurement light. and The distance calculation unit calculates the distance to the object being measured based on the optical path difference between the reference light reflected from the reference surface and the measurement light reflected from the object being measured. The convergence section includes: The first lens is through which the measuring light enters. The moving part moves the first lens along the optical axis. The position detection unit detects the position of the first lens. The second lens directs the measuring light emitted from the first lens toward the object to be measured. A correspondence calculation unit, when the converging part is focused on the object to be measured, calculates the correspondence between the focal position of the converging part and the position of the first lens based on the position of the first lens and the distance from the object to be measured calculated by the distance calculation unit, wherein... The control unit controls the moving unit and moves the first lens to adjust the focal point position where the second lens converges the measurement light; The control unit moves the first lens to satisfy the following equation calculated by the correspondence calculation unit, where f1 is the focal length of the first lens, f2 is the focal length of the second lens, d is the inter-lens distance between the first and second lenses, and z is the converging distance from the second lens to the focal point where the measuring light converges at the converging unit. The correspondence calculation unit uses the following equations to calculate the following values: a) the inter-lens distance d1 and convergence distance z1 at a first position on the object to be measured; and b) the inter-lens distance d2 and convergence distance z2 at a second position, wherein L1 is the first distance from the measuring device to the first position on the object to be measured, calculated by the distance calculation unit, and L2 is the second distance from the measuring device to the second position on the object to be measured, calculated by the distance calculation unit. ； ； The correspondence calculation unit also calculates the internal optical path difference by subtracting the convergence distance z1 of the first position on the object to be measured from the first distance L1, or by subtracting the convergence distance z2 of the second position on the object to be measured from the second distance L2. The internal optical path difference represents the optical path difference between the measuring light and the reference light inside the measuring device.

11. A measurement method, comprising the following steps: Output laser beam; The laser beam is divided into: (i) a reference beam, which is a part of the laser beam, for illuminating a reference surface, and (ii) a measurement beam, which is at least a part of the remaining portion of the laser beam, for illuminating the object to be measured; The measurement light is focused onto the object to be measured by using a converging section having a first lens and a second lens; Interference signals are detected based on the optical path difference between the reference light reflected from the reference surface and the measurement light reflected from the object to be measured. Calculate the distance to the object to be measured, which corresponds to the phase difference of the interference signal; Based on the position of the first lens and the calculated distance to the object to be measured, the correspondence between the focal position of the converging part and the position of the first lens is calculated; in The gathering includes: Allow the measuring light to enter the first lens. The measuring light emitted from the first lens is directed towards the object to be measured through the second lens. Move the first lens so that the focal point of the second lens converging the measurement light is aligned with the object to be measured, while maintaining a constant internal optical path difference. This internal optical path difference represents the optical path difference between the optical path from the position where the laser splits into the measurement light to the second lens and the optical path from the position where the laser splits into the reference light to the reference surface. and Detect the position of the first lens.

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